Polyolefin fibers are typically made by spinning a fluid composition comprising polyolefin from an extrusion die. Polyolefin fibers made in this way may be made into a multifilament yarn by e.g. twisting a plurality of fibers. Polyolefin fibers may also be used as a precursor for making further products, including a monofilament-like fiber. One way of doing this is to fuse a plurality of precursor polyolefin fibers into one final product. In EP 0740002 B1, a process for making a fishing line from yarns of filamentous materials is described, wherein a braided, twisted, or twisted and plied fishing line made from yarns of gel spun polyolefin filaments, is exposed to a temperature within the melting point range of said polyolefin for a time sufficient to at least partially fuse adjacent filaments while stretching said line at a stretching ratio within the range from 1.01 to 2.5. The yarns applied in this process are continuous multi-filament yarns, more specifically such yarns made by so-called gel spinning of ultra-high molar mass polyethylene (UHMwPE), for example yarns commercially available under the names Spectra® or Dyneema®.
In the known processes, the yarn or the fiber is made from multiple fibers. Possible differences in the properties between the precursor fibers may affect the properties of the final product. Moreover, the parts of the final product which are originally the interfaces between the precursor fibers may have different properties from the other parts of the product.